Supporting Information

Porous Nafion nanofiber composite membrane with vertical

pathways for efficient through-plane proton conduction

Jingtao Wanga, Ping Lia, Yafang Zhanga, Yarong Liua, Wenjia Wua,b,*, Jindun Liua

a School of Chemical Engineering and Energy, Zhengzhou University, Zhengzhou 450001, P. R. Chinab Department of Civil and Environmental Engineering, Center for the Environmental Implications of NanoTechnology (CEINT), Duke University, Durham, North Carolina 27708, USA

*To whom correspondence should be addressed. E-mail: wenjiawu@zzu.edu.cn

Fig. S1. Chemical structure of (a) long alkyl chain contained [C8mim][Tf2N] and (b) short alkyl chain contained [C2mim][Tf2N].

Fig. S2. SEM images of (a) NF/PAN and (b) NF/PAN-C8-20(with).

Fig. S3. High-resolution SEM images of (a) NF/PAN-C8-15, (b) NF/PAN-C8-20, (c) NF/PAN-C8-

25, (d) NF/PAN-C2-15, (e) NF/PAN-C2-20, and (f) NF/PAN-C2-25.

Fig. S4. Nitrogen adsorption/desorption isotherms of (a) NF/PAN and NF/PAN-C8-X and (b) NF/PAN and NF/PAN-C2-X.

100 200 300 400 500 600 700 80040

60

80

100

Wei

ght (

%)

Temperature (oC)

NF/PAN NF/PAN-C2-15 NF/PAN-C2-20 NF/PAN-C2-25

b

0.0

0.5

1.0

1.5

2.0 NF/PAN-C2-25

IEC

(mm

ol g

-1)

NF/PANc

48h24h12h6h2400 2100 1800 1500 1200 900 600

*571*

Tran

smitt

ance

(a.u

.)

Wave number (cm-1)

1195

NF/PAN

NF/PAN-C2-25(with)

NF/PAN-C2-25

1058(SO3H)a

Fig. S5. (a) FTIR spectra of NF/PAN, NF/PAN-C2-25(with), and NF/PAN-C2-25. (b) TGA curves of NF/PAN and NF/PAN-C2-X. (c) dynamic IEC values of NF/PAN and NF/PAN-C2-25 as a

function of testing time.

Fig. S6. Stress–strain curves of CS/NF/PAN and CS/NF/PAN-C2-X.

Fig. S7. IEC values of CS/NF/PAN and CS/NF/PAN-C2-X.

Fig. S8. (a) Water uptake and (b) volume swelling of CS/NF/PAN and CS/NF/PAN-C8-X.

Fig. S9. (a) Water uptake and (b) volume swelling of CS/NF/PAN and CS/NF/PAN-C8-X.

Fig. S10. TGA curves of CS/NF/PAN and CS/NF/PAN-C8-X.

Fig. S11. Arrhenius-plots of (a) perpendicular conductivity (σ⊥) and (b) parallel conductivity (σ∥) of CS/NF/PAN and CS/NF/PAN-C8-X under 0 % RH.

0 30 60 90

50

100

150

200

250RH=60%RH=40%RH=20%

Con

duct

ivity

σ ⊥(m

S cm

-1)

Time(min)

CS/NF/PAN CS/NF/PAN-C2-20 CS/NF/PAN-C2-15 CS/NF/PAN-C2-25

30 45 60 75 90 105 1200

50

100

150

Through-plane 0 % RH，

Membrane Ea / kJ mol-1

Con

duct

ivity

σ⊥

(mS

cm-1

)

Temperature (oC)

CS/NF/PAN 26.1 CS/NF/PAN-C2-15 12.8 CS/NF/PAN-C2-20 11.4 CS/NF/PAN-C2-25 10.7

30 45 60 75 90 105 1200

50

100

150

200

250

300

In-plane, 0 % RH

Membrane Ea / kJ mol-1

Con

duct

ivity

σ∥ (

mS

cm-1

)

Temperature (oC)

CS/NF/PAN 7.31 CS/NF/PAN-C2-15 5.26 CS/NF/PAN-C2-20 4.26 CS/NF/PAN-C2-25 3.86

b c

d e f

a

0

50

100

150

200

250 σ∥

Con

duct

ivity

(mS

cm-1

)

σ⊥

1.5

2.0

2.5

3.0 σ∥ /σ⊥ values

CS/NF/PAN-C2-25CS/NF/PAN-C2-20CS/NF/PAN-C2-15CS/NF/PAN

σ∥ /σ⊥

0 20 40 60 80 100

50

100

150

200

250

300

Through-plane, 80 oC

Con

duct

ivity

σ ⊥(m

S cm

-1)

RH(%)

CS/NF/PAN CS/NF/PAN-C2-15 CS/NF/PAN-C2-20 CS/NF/PAN-C2-25

0

50

100

150

200

250

300

350

30 40 50 60 70 80 90

Con

duct

ivit

y σ ⊥

(mS

cm-1

)

Temperature（°C）

CS/NF/PANCS/NF/PAN-C₂-15CS/NF/PAN-C₂-20CS/NF/PAN-C₂-25

Fig. S12. CS/NF/PAN and CS/NF/PAN-C2-X: (a) Temperature-dependent perpendicular conductivity (σ⊥) under 100% RH; (b) RH-dependent perpendicular conductivity (σ⊥) at 80 oC; (c)

Time-dependent perpendicular conductivity (σ⊥) at 80 oC and different RH; (d) Temperature-dependent perpendicular conductivity (σ⊥) at 0% RH; (e) Parallel conductivity (σ∥) at 0% RH; (f)

Perpendicular conductivity (σ⊥), parallel conductivity (σ∥), and transfer anisotropy coefficient (σ∥/σ⊥) at 120 oC and 0% RH.

Fig. S13. Arrhenius-plots of (a) perpendicular conductivity (σ⊥) and (b) parallel conductivity (σ∥) of CS/NF/PAN and CS/NF/PAN-C2-X under 0 % RH.

Table S1. Thickness of the membranes.

MembraneCS/NF/PAN CS/NF/PAN-

C8-15

CS/NF/PAN-

C8-20

CS/NF/PAN-

C8-25

CS/NF/PAN-

C2-15

CS/NF/PAN-

C2-20

CS/NF/PAN-

C2-25

Thickness

(μm)90 92 99 96 92 98 93

Table S2. Proton conduction behaviors of other NFCMs in the literatures.

Samples σ∥(mS cm-1) σ⊥(mS cm-1) σ∥/σ⊥ Conditions Ref.

Electrospun SPPESK membrane80 7 11.4 30 oC, 100% RH

1165 37 4.50 80 oC, 100% RH

Electrospun 6FDA-BDSA-r-APPF membrane 212 81 2.62 90 oC, 98% RH 2

S-PS fiber/Nafion hybrid membranes 180 - - 100 oC, 80% RH 3

S-ZrO2 fiber-Nafion hybrid membrane 310 - - 80 oC, 100% RH 4

Electrospun F-SPFEK composite membrane - 61 - 80 oC, 100% RH 5

Electrospun PVDFNF-Nafion membrane - 91 - 90 oC, 95% RH 6

Electrospun SPES + Nafion - 88 - 25 oC, 95% RH 7

Phy-doped PBINf and Nafion matrix 130 - - 80 oC, 95% RH 8

Nafion/PSSA-g-PVDFNF membrane - 106 - 95 oC, 95% RH 9

Nonwoven PAN resin + SPAES50 copolymer 164 - - 80 oC, 100% RH 10

Nonwoven PI + GPTMS / H3PO4 mixture 166 - - 80 oC, 80% RH 11

Nonwoven PAI-PTM + SPAES 110 - - 80 oC, 100% RH 12

Electrospun PFSA + (NOA) 63160 - - 80 oC, 80% RH

1348 - - 80 oC, 50% RH

SPS/PEO fiber + PDMS 100 - - 25 oC, 98% RH 14

SiO2/SPEEK composite nanofiber + Nafion - 77 - 90 oC, 100% RH 15

SPAES nanofiber + silicate 60 - - 30 oC, 100% RH 16

Polysulfone/POSS Nanofiber+NOA 94 - - 30 oC, 80% RH 17

Pd-SiO2 nanofiber+Nafion 129 - - 25 oC, 100% RH 18

Nafion nanofiber+ (NOA) 63 80 - - 25 oC, 100% RH 19

SPEEK nanofiber+CS - 60 - 120 oC, 0% RH 20

Electrospun SPPESK + SPPESK matrix 213 - - 120 oC, 100%RH 21

PFSA/SPOSS/PAA+NOA6321 - - 120 oC, 20% RH

22107 - - 120 oC, 50% RH

SPEEK nanofibers + Nafion matrix 90 - - 20 oC, 100% RH 23

BPPO nanofiber+SPPO matrix 80 - - 25 oC, 100% RH 24

PBI nanofiber-reinforced PBI membranes 170 - - 160 oC, 0% RH 25

CS/NF/PAN180

-

56

97

3.19

-

120 oC, 0% RH

90 oC, 100% RHthis work

CS/NF/PAN-C8-25301

-

129

294

2.33

-

120 oC, 0% RH

90 oC, 100% RHthis work

CS/NF/PAN-C2-25270

-

150

307

1.80

-

120 oC, 0% RH

90 oC, 100% RHthis work

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